1. Field of the Invention
The present invention relates to a communication apparatus for securing communication resources corresponding to a requested quality, a communication method thereof, and a record medium thereof.
2. Description of the Related Art
As Internet/Intranet is becoming common, distributed systems are drastically popularizing. However, since the systems are becoming complicated and large-scaled and component-ware is being used, it is very difficult to grasp the entire program and entire system. Thus, it is difficult to numerically analyze a system for simulating and modeling the system. In other words, when a system is developed, it cannot be satisfactorily designed and developed. A major cause that prevents an evaluation of the system performance is in that a plurality of jobs share one resource. Many users share a network resource and a computing resource. Since each user has a different optimizing standard, it is difficult to predict a system performance. When the system performance is predicted, the user also requires the worst data of the system performance as well as the average data thereof. However, in a complicated system that a plurality of users share, such worst data tends to exceed engineering experience data. Thus, in this case, a logical analysis does not well work. In a real experiment, since data that creates the worst situation cannot be prepared, the operational worst situation cannot be simulated. Consequently, the performance evaluation/prediction problem becomes complicated. For example, in the conventional computer communication field such as Internet, the best effort system is employed. In the best effort system, a communication resources are equally shared by a plurality of users. Thus, since a communication of a particular user is affected by communications of other communication users, it is difficult to secure a required band for the particular user. To solve this problem, the transmission rate of data is measured on the receive side. The obtained information is fed back to the sender side. Thus, the sender side controls the transmission rate of the data. When the communication rate is low, the sender side decreases information. Consequently, a data transmission at a constant transmission rate is accomplished. However, in this method, to send feedback information, another line is required. In addition, regardless of the content of the transmission data, the information is flatly decreases. This method is referred to as a data decreasing method.
As band securing type communication systems other than the best effort system, ATM (Asynchronous Transfer Mode) communication system and RSVP (Resource Reservation Protocol) system are being studied. However, in these systems, as the types of data handled on networks increase, regardless of features of data, required communication bands are successively assigned to users on "first come, first served" basis. Thus, when a required communication band cannot be secured, the communication request is refused. Consequently, the user should wait until the communication resource becomes available.
As described above, in the data decreasing method, it is difficult to secure a required band in the computer communication field. In this method, another line is required. In addition, information is flatly decreased regardless of the content of the data. On the other hand, in the ATM system and the RSVP system, when a required band cannot be secured, the request is refused. Thus, the user should wait until the communication resource becomes available.
When limited communication resources are shared by many unspecified users, priority levels that are in common with the network should be designated. Corresponding to the priority levels, the resources should be equally assigned to the users.
For example, when picture data to be sent/received is used for a news material, if the real-time transmission of the data is the most important and the picture quality thereof is not so important, it is necessary to decrease the data corresponding to the variation of the communication amounts of routers and servers. Thus, other communication requests can be satisfied and many users can be provided with services.
In contrast, when data to be sent/received is used for movie information, if the picture quality is important than the real time transmission, as long as available transmission start time is provided, the user can wait until the available transmission time. To do that, reservations for communication resources should be made on time axis.
In addition, in the case of data of a movie, the data may contain a climax portion that requires high picture quality and a normal portion that does not require high picture quality. In this case, if information is flatly decreased, the worth of the movie data is lost. Thus, the decreasing method of information should be dynamically varied corresponding to the situation.